Real Estate wholesaling occurs when a party (the "wholesaler") contracts with a home seller, markets the home to potential buyers, and then assigns the contract to one of them. The wholesaler makes a profit, which is the difference between the contracted price with the seller and the amount paid by the buyer. The goal in real estate wholesaling is to sell the home before the contract with the original homeowner expires.

Wholesaling offers the investor an opportunity to acquire real property at below market value which presents the opportunity for better rental income or higher profit margins on renovation projects.  However, these opportunities generally require a much quicker closing period than traditional real estate transactions. 
Credit: Troy Segal @ Investopedia